[LeArc] Forecast Discussion : MLI@ 12/10/02 2:46:59 PM

[Richard R. Sample]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 102100
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 PM CST TUE DEC 10 2002

STRATUS THAT DEVELOPED/ADVECTED OUT KS THIS MORNING INTO WRN HALF OF 
IA HAS BEEN SLOWLY ERODING THIS AFTERNOON.  LATEST VIS IMAGES 
SHOWING THE STRATUS IN IA JUST EAST OF THE MO RIVER.   TEMPS OUTSIDE 
OF THE STRATUS HAVE WARMED NICELY TODAY IN SWLY FLOW BETWEEN NRN 
PLAINS TROF AND SFC RDG NEAR THE OHIO RIVER.  SPLIT H5 FLOW  
CONTINUES OVER U.S.  CUTOFF H5 LOW OVER AR AT 12Z PROGGED TO 
CONTINUE E WILL LITTLE IMPACT ON CWA.  UP STREAM...NEXT SYSTEM 
IMPACT REGION STILL APPROACHING NW PACIFIC COAST. 

MAIN SHORT TERM CONCERNS WILL BE STRATUS AND FOG DEVELOPMENT TONIGHT 
INTO WEDNESDAY.  MESOETA APPEARS TO HAVE A GOOD HANDLE ON THE 925MB 
RH ASSOCIATED WITH THE STRATUS FIELD.  MESOETA BRINGS THE HIER RH E 
TONIGHT OVER THE WRN THIRD OF CWA.  THIS IS SUPPORTED BY 30+ SFC 
DEWPOINTS AS FAR EAST AS KCID AT 20Z.  ALSO GOES SOUNDINGS EAST OF 
STRATUS FIELD INTO WRN CWA SHOW VERY MOIST LAYER AROUND 950MB WHICH 
SUPPORTS STRATUS DEVELOPMENT AS LOW LEVELS COOL TONIGHT.  SINCE 
TEMPS HAVE WARMED SO MUCH THIS AFTERNOON...FEEL IT WILL TAKE AWHILE 
FOR THE CLOUDS/FOG TO DEVELOP...PROBABLY AFTER MIDNIGHT.  THEREFORE 
HAVE HELD OFF ON DENSE FOG ADVISORY.  ONE MAY BE NEED LATE TONIGHT 
IN THE FAR WEST AND WILL ISSUE UPDATED HWO CONCERNING THE FOG 
THREAT.  WILL TREND TEMPS IN THE WEST TO...OR ABOVE WARMER MET 
NUMBERS WHILE EASTERN COUNTIES WILL TREND TOWARD COOLER MAV.  925 
FLOW VEERS TO A MORE SOUTHWESTERLY DIRECTION BY WEDNESDAY 
AFTERNOON...WHICH SHOULD PUSH STRATUS FIELD EAST.  META SHOWING LOTS 
OF LOW LEVEL RH WED NIGHT INTO THURSDAY...AND PLAN TO CONTINUE 
MENTION OF FG/DZ ALREADY IN FCST. AGAIN COOLER MAV TEMPS LOOK 
REASONABLE IN THE WEST WHERE CLOUDS WILL INHIBIT RECOVERY. TEMPS IN 
THE EAST SHOULD FAVOR THE WARMER MET NUMBERS. WILL STICK WITH 
WARMER MET NUMBERS MOST AREAS WEDNESDAY NIGHT WITH EXPECTED CLOUD 
COVER. 

MODELS STILL SHOWING WIDE VARIETY OF SOLUTIONS WITH RESPECT TO 
TIMING AND LOCATION FOR SYSTEM PROGGED TO MOVE THROUGH THE 
PLAINS/MID-LOWER MS VALLEY AT THE END OF THE WEEK.  GFS CONTINUES TO 
BE THE STRONGEST AND MOST OMINOUS FOR CWA. 12Z GFS CLOSES OFF AN H5 
LOW OVER OVER MT BY 12Z THURSDAY THEN TRACKS SE ACROSS SRN MO/IL 
FRIDAY WITH SFC LOW MOVING ALONG I70 FRIDAY.  THIS TRACK SUGGESTS A 
SIGNIFICANT PRECIP EVENT FOR AT LEAST THE SOUTHERN HALF OF THE CWA.  
ETA/ECMWF/UKMET/CANADIAN ON THE OTHER HAND EITHER CLOSE OFF SYSTEM 
LATER THAN GFS OR NOT AT ALL AND FAVOR A MORE SOUTHERN TRACK FOR THE 
SURFACE LOW...CLOSER TO THE PROGGED H850 BAROCLINIC ZONE.  FOR NOW 
WILL CONTINUE WITH LOW CHANCE POPS FOR THE EVENT.  IF THE GFS 
VERIFIES THEN SNOW WILL BE A POSSIBLITY WITH GFS SHOWING A POOL OF 
-3C AIR AT H850 JUST NORTH OF THE SFC LOW TRACK.  

EXTENDED (SAT-TUE)
DUE TO INCONSISTENCIES NOTED ABOVE IN THE HANDLING OF THE SYSTEM AT 
THE END OF THE WEEK...WILL KEEP SATURDAY DRY.  ALTHOUGH IF GFS IS 
RIGHT...PCPN COULD LINGER INTO SATURDAY MORNING.   FOR THE REST OF 
THE WEEKEND AND EARLY NEXT WEEK...FAST ZONAL FLOW ON SUNDAY 
TRANSITIONS INTO BROAD H5 TROF OVER WRN HALF OF THE COUNTRY BY 
TUESDAY.  THIS KEEPS REGION UNDER SWLY SFC FLOW...SUPPORTING ABOVE 
NORMAL TEMPS.  GFS PRINTING OUT SOME LIGHT PCPN LATE MONDAY AND 
TUESDAY...HOWEVER... FORCING NOT EVIDENT YET AND IT MAY BE MORE OF A 
REFLECTION OF HIGH LOW LEVEL RH.  WILL CONTINUE TO KEEP MON/TUES DRY.


IA...NONE.
IL...NONE.
MO...NONE.
DLF